The present disclosure relates generally to a system and method for adjusting image on paper (IOP) registration in a printing device. In particular, the present disclosure relates to in-line sensing and measuring IOP registration in a printing device.
Printing devices, including electrophotographic printing devices, require a system and method for achieving proper IOP registration. In a xerographic printing device, IOP registration may be achieved by controlling registration of an imageable surface, such as a photoreceptor belt, an intermediate transfer belt if any, images to be transferred, and the substrate to which the image will be transferred.
First, IOP misregistration of an image transferred to a substrate is measured. Corrections are made, such as by adjusting parameters related to the transfer of the images to or from the image bearing surface in accordance with the determined misregistration. The adjusting may be performed, for example, by controlling parameters related to operation of a raster output scanner (ROS) imaging system or other latent or visible image forming system, operation of a paper registration system, and/or movement of the imageable surface.
IOP misregistration may be determined by measuring image offsets in the process and cross-process directions, image magnification in the process and cross-process directions, and image skew. The process direction is the direction in which the substrate onto which the image is transferred and developed moves through the image transfer and developing apparatus. The cross-process direction, along the same plane as the substrate, is substantially perpendicular to the process direction. Image skew is the angular deviation of the raster output scanner scan lines from the process direction of the substrate, or a line normal to the process direction of the marked substrate.
In prior art devices measurements such as those listed above may be made by printing a diagnostic image and taking measurements of the printed image. The printed image may be measured by hand using a magnifying eye loupe or may be scanned in and performed automatically. The results are then provided, typically manually, to a control system of the printing device. The control system uses the measurements to make adjustments for correcting any detected misregistration. The above process is performed offline (not inline), and requires human intervention, with the potential for human error.
There are prior art systems which perform IOP misregistration measurements in-line, e.g., as the substrate is moved through the printing device for marking of the substrate. A photo-detector array or CCD array is provided which acquires and records images of a substrate after a diagnostic image is transferred to the substrate. The images are processed, including taking measurements in the process and cross-process directions. The resultant measurements are provided to the control system of the printing device and used for making adjustments for improving IOP misregistration. The photo-detector arrays and CCD arrays add substantial cost to the printing device. Each image acquired includes an array of information which consumes substantial storage and processing resources.
To overcome the drawbacks in the prior art, it is an aspect of the present disclosure to provide a system and method for in-line measuring and correcting of IOP misregistration using simple inexpensive point sensors.
It is further an aspect of the present disclosure to provide a system and method in which the storing and processing of the sensor output consumes minimal resources.